Large collective motions regulate the functional properties of glutamate transporter trimers

Glutamate transporters clear synaptically released glutamate to maintain precise communication between neurons and limit glutamate neurotoxicity. Although much progress has been made on the topology, structure, and function of these carriers, few studies have addressed large-scale structural motions collectively associated with substrate transport. Here we show that a series of single cysteine substitutions in the helical hairpin HP2 of excitatory amino acid transporter 1 form intersubunit disulfide cross-links within the trimer. After cross-linking, substrate uptake, but not substrate-activated anion conductance, is completely inhibited in these mutants. These disulfide bridges link residue pairs > 40 Å apart in the outward-facing crystal structure, and can be explained by concerted subunit movements predicted by the anisotropic network model (ANM). The existence of these global motions is further supported by the observation that single cysteine substitutions at the extracellular part of the transmembrane domain 8 can also be cross-linked by copper phenanthroline as predicted by the ANM. Interestingly, the transport domain in the un-cross-linked subunit of the trimer assumes an inward-facing orientation, suggesting that individual subunits potentially undergo separate transitions between outward- and inward-facing forms, rather than an all-or-none transition of the three subunits, a mechanism also supported by ANM-predicted intrinsic dynamics. These results shed light on how large collective motions contribute to the functional dynamics of glutamate transporters.     

BCG response prediction with cytokine gene variants and bladder cancer: where we are?

Purpose  

Bladder cancer (BC) is one of the most widespread cancers afflicting men and women and also has major philosophical impact on health care worldwide. Despite elaborate characterization of the risk factors and treatment options, BC is still a major epidemiological problem worldwide and its incidence lingers to upswing each year. Over the last three decades, intravesical immunotherapy with the biological response modifier Mycobacterium bovis–Bacillus Calmette Guerin (BCG) has been established as the most effective adjuvant treatment for averting local recurrences and tumor progression following transurethral resection of non-muscle-invasive bladder cancer.     

Pulmonary vein antrum isolation for atrial fibrillation on therapeutic coumadin: special considerations

Pulmonary vein antrum isolation (PVAI) has emerged as an effective treatment for drug-refractory atrial fibrillation (AF). However, thromboembolic events are important complications of this approach. Management of anticoagulation is essential to prevent thromboembolic complications and avoid bleeding complications. The purpose of this review is to outline the general principles followed at our AF centers to address the important issue of pre-, peri-, and postprocedural anticoagulation strategies during PVAI of AF. We initiate warfarin therapy prior to the ablation procedure and continue it through the procedure. Prior work has demonstrated that continuation of therapeutic warfarin during the radiofrequency catheter ablation reduces the risk of periprocedural stroke/transient ischemic attack without increasing the risk of hemorrhagic events. In fact, a strategy that interrupts warfarin anticoagulation may increase the risk of stroke, even with bridging with enoxaparin. Data from our work have shown that minor bleeding was more frequent in the patients bridged with heparin or enoxaparin. There was no significant difference in incidence of major bleeding complications among the patients with a therapeutic level of international normalized ratio (INR) compared with patients for whom bridging therapy was used. Furthermore, the strategy of ablation during a therapeutic INR could be more economical compared with bridging therapy with enoxaparin. Continuation of therapeutic warfarin during ablation of AF may be the best strategy, especially in patients with nonparoxysmal AF, patients with higher thromboembolic risk scores, and patients who require extensive ablation during PVAI of AF.     

The reproducibility of heart rate recovery after treadmill exercise test

Background: Although predictive value of heart rate recovery (HRR) has been tested in large populations, the reproducibility of HRR in treadmill exercise test has not been assessed prospectively. This prospective study examined whether HRR index has test–retest stability in the short term. Methods: A total of 52 healthy volunteers without cardiovascular risk factors (mean age, 30 ± 10 years, 30 females) underwent standardized graded treadmill exercise test, and the test was repeated on the 7th and the 30th days. The subjects’ maximal heart rates and the decrease of heart rate from the peak exercise level to the level of 1, 2, 3, 4, and 5 minutes after the termination of the exercise were examined on each test, and heart rates for each minute from the first, second, and third tests were compared for each individual. Results: The maximal heart rates on the 1st, 7th, and the 30th days were 179 ± 11, 177 ± 10, 178 ± 10 beats/min, respectively [P = 0.07, intraclass correlation coefficient (ICC) = 0.92], and the 1st minute HRR indices after peak exercise were 33 ± 10, 33 ± 10, 33 ± 11, respectively (P = 0.66, ICC = 0.88). There was no statistical difference in the 2nd, 3rd, 4th, and 5th minute heart rates of the recovery phase among the 1st, 7th, and 30th day treadmill exercise tests, either. Conclusion: Maximal heart rates and the decline of heart rate to the 5th minute on recovery phase after treadmill exercise test have short‐term reproducibility. Ann Noninvasive Electrocardiol 2011;16(4):365–372     

Peroxyl-induced oxidative stress in aging erythrocytes of rat

This study aims at determining the possible changes in intracellular calcium (Ca_i²⁺), plasma membrane calcium ATPase (PMCA) activity and phosphatidylserine (PS) along with glutathione (GSH) level in response to an oxidant challenge in vitro. Erythrocytes were isolated on Percoll and incubated with 2, 2′azobis (2-aminopropane) hydrochloride (AAPH) as well as with vitamin C preceding AAPH incubation. Membrane integrity in terms of hemolysis was negatively related to acetylcholine esterase (AChE) activity with the extent of reduction under OS being higher in the old erythrocyte than in the young. A divergent pattern was seen towards lower PMCA and higher (Ca_i²⁺) in the young and old cells. However, the PMCA activity in the stressed young cell was high when pre-treated with vitamin C. PS externalization in the young under OS is perhaps analogous to normal aging, with vitamin C preventing premature death. These findings suggest that young erythrocytes may benefit from vitamin C in therapies addressed towards the mechanisms underlying the reduced effects of OS.     

In vitro antioxidant activities of selected seaweeds from Southeast coast of India

ObjectiveIn vitro antioxidant activities of three selected Indian seaweeds viz., Halimeda tuna (H. tuna), Turbinaria conoides (T. conoides) and Gracilaria foliifera (G. foliifera) were evaluated.MethodsTotal antioxidant activity, total phenolic content, and reducing power of crude methanol and diethyl ether extracts were determined.ResultsTotal phenolic content and total antioxidant activity were higher (1.231±0.173 mg GAE/g, 1.675± 0.361 mg GAE/g) in T. conoides respectively. Reducing power of crude methanol extract increased with concentrations of the extract. The Fourier transform-infra red spectrum analysis revealed the presence of polyphenolic signals. The seaweed extracts displayed moderate antioxidant activity compared to gallic acid standard.ConclusionsThe seaweeds could be considered for curing diseases from oxidative deteriorations.